Deck 105: Power Brake Unit Operation, Diagnosis, and Service

Question 1

Two technicians are discussing vacuum brake boosters. Technician A says that a low, soft brake pedal is an indication of a defective booster. Technician B says that there should be at least two power-assisted brake applications after the engine stops running. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Answer 1

Technician B only

Question 2

Technician A says that to check the operation of a vacuum brake booster, the brake pedal should be depressed until the assist is depleted and then start the engine. Technician B says that the brake pedal should drop when the engine starts, if the booster is okay. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Answer 2

Both technicians A and B

Question 3

Brake pedal feedback to the driver is provided by the ________.

A)Reaction system
B)Charcoal filter unit
C)Vacuum diaphragm
D)Vacuum check-valve operation

Answer 3

Reaction system

Question 4

The proper operation of a vacuum brake booster requires that the engine be capable of supplying at least ________.

A)21 in. Hg vacuum
B)15 in. Hg vacuum
C)17 in. Hg vacuum
D)19 in. Hg vacuum

Question 5

The purpose of the charcoal filter in the vacuum hose between the engine and the vacuum brake booster is to ________.

A)Filter the air entering the engine
B)Trap gasoline vapors to keep them from entering the booster
C)Direct the vacuum
D)Act as a one-way check valve to help keep a vacuum reserve in the booster

Question 6

A defective vacuum brake booster will cause a ________.

A)Slight hiss noise when the brake pedal is depressed
B)Low brake pedal
C)Hard brake pedal
D)Soft (spongy) brake pedal

Question 7

An accumulator such as that used on hydraulic brake boosters ________.

A)Provides a reserve in the event of a failure
B)Works against engine vacuum
C)Provides higher force being fed back to the driver's foot
D)Reduces brake pedal noise

Question 8

The first step in diagnosing a Hydro-Boost problem is ________.

A)A pressure test of the pump
B)A volume test of the pump
C)A thorough visual inspection
D)To tighten the power steering drive belt

Question 9

A brake pedal feels spongy when depressed. Technician A says that a defective hydraulic brake booster could be the cause. Technician B says that a defective vacuum brake booster could be the cause. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Question 10

If the engine stops running, the Hydro-Boost will not be able to provide any power assist for the brakes.

Question 11

Two technicians are discussing vacuum brake boosters. Technician A says that when the engine is running and the driver's foot is off the brake pedal, a vacuum is present on both sides of the booster diaphragm. Technician B says that when the brakes are in the applied position, vacuum is present on the front side of the diaphragm. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Question 12

To provide the driver with a sense of "feel" during braking, vacuum boosters use a ________.

A)Diaphragm spacer
B)Vacuum diverter
C)Pressure restrictor
D)Reaction disc

Question 13

A hydraulically operated booster unit stores fluid under pressure by means of ________.

A)An actuator
B)A pressure chamber
C)An accumulator
D)A boost piston

Question 14

A common source of vacuum for boosters used on diesel engines is ________.

A)Exhaust manifold
B)Auxiliary vacuum pump
C)Carburetor
D)Intake manifold

Question 15

Technician A says when the brakes are applied in a vacuum booster, the vacuum control valve is sealed.Technician B says the vacuum control valve is opened. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Question 16

When the Hydro-Boost is in the release phase ________.

A)The vent port is opened
B)The fluid port to the power chamber is closed
C)Both A and B
D)Neither A nor B

Question 17

The booster operation test determines if the booster is ________.

A)Receiving adequate vacuum
B)Creating brake application force
C)Both A and B
D)Neither A nor B

Question 18

Technician A says the vacuum supply test involves inspecting the vacuum supply hose for kinks. Technician B says the test involves checking the level of vacuum supplied by the engine or vacuum pump. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Question 19

Pushrod adjustment is checked with a ________.

A)Variable gauge
B)Feeler gauge
C)Either A or B
D)Neither A nor B

Question 20

The Hydro-Boost brake booster uses what type of fluid to multiply brake pedal force?

A)Power steering fluid
B)Transmission fluid
C)Brake fluid
D)None of these

Question 21

The brake assist system (BAS) is activated ________.

A)On the rear brakes
B)Only in the rain
C)Whenever the brakes are applied
D)During a panic stop

Question 22

What component is the technician holding in this photograph?

A)Fluid plug
B)Check valve
C)Vacuum sensor
D)Vacuum elbow

Question 23

The pushrod length should be checked whenever a new master cylinder is installed.

Question 24

Some vacuum boosters have more than one power diaphragm.

Question 25

A Hydro-Boost unit uses the power steering pump as a source of power.